"Watching the Mac Pro come together in Austin yesterday,thanks to a team loaded with American manufacturing expertise," his update read.

Apart from the lack of a space between the comma and the word "thanks", and the shameless US plug, it initially looks like a perfectly well-constructed, if a little dull, tweet.

However, Cook decided to attach an image to his update, and he did not choose wisely.

The picture (above) shows him with a bunch of factory workers, standing before a pair of iMacs which appear to be running the Windows XP OS. Other Twitter users were quick to point out the gaffe, with one replying, "the iMacs in the BG are running WINDOWS. How dare you."

Those who tuned in to the WWDC keynote last week will remember that Cook took it upon himself to heavily criticise both Microsoft's and Google's operating systems.

Cook mocked Microsoft for the lukewarm reaction to Windows 8 and rounded on Android for its fragmentation, saying, "Some [customers] are on [Android] from four years ago – that's like ancient history!"